Fumonisin [KLH]

Fusaric acid (FA), a mycotoxin contaminant of maize, displays toxicity in plants and animals; however, its epigenetic mechanism is unknown. DNA methylation, an epigenetic modification that regulates gene expression, is mediated by DNA methyltransferases (DNMTs; DNMT1, DNMT3A, and DNMT3B) and demethylases (MBD2). The expression of DNMTs and demethylases are regulated by promoter methylation, microRNAs (miR-29b) and post-translational modifications (ubiquitination). Alterations in these DNA methylation modifying enzymes affect DNA methylation patterns and offer novel mechanisms of FA toxicity. We determined the effect of FA on global DNA methylation as well as a mechanism of FA-induced changes in DNA methylation by transcriptional (promoter methylation), post-transcriptional (miR-29b) and post-translational (ubiquitination) regulation of DNMTs and MBD2 in the human hepatocellular carcinoma (HepG2) cell line. FA induced global DNA hypomethylation (p < 0.0001) in HepG2 cells. FA decreased the mRNA and protein expression of DNMT1 (p < 0.0001), DNMT3A (p < 0.0001), and DNMT3B (p < 0.0001) by upregulating miR-29b (p < 0.0001) and inducing promoter hypermethylation of DNMT1 (p < 0.0001) and DNMT3B (p < 0.0001). FA decreased the ubiquitination of DNMT1 (p = 0.0753), DNMT3A (p = 0.0008), and DNMT3B (p < 0.0001) by decreasing UHRF1 (p < 0.0001) and USP7 (p < 0.0001). FA also induced MBD2 promoter hypomethylation (p < 0.0001) and increased MBD2 expression (p < 0.0001). Together these results indicate that FA induces global DNA hypomethylation by altering DNMT promoter methylation, upregulating miR-29b, and increasing MBD2 in HepG2 cells.

Here we demonstrate a noncompetitive idiometric nanobodies phage immunoassay for the determination of FB1, utilizing two types of anti-idiotypic nanobody, that is specific for different epitopes within the hypervariable region of the primary mAb. Three alphatype anti-idiotypic nanobodies were obtained from a naive nanobodies phage-display library. A noncompetitive idiometric immunoassay was established with a combination of betatype anti-idiotypic nanobody and phage-displayed alphatype anti-idiotypic nanobody. The half-maximal saturation of the signal value (SC50) was 0.68 ng/mL, with the limit of detection (LOD) was 0.19 ng/mL. When the noncompetitive assay was compared to the competitive ELISA (LOD = 3.41 ng/mL), an over 17-fold improvement in sensitivity was observed. A correlation (R-2) was 0.988 between the data of the noncompetitive assay and LC-MS/MS for the determination of FB1 in cereal samples. The noncompetitive idiometric immunoassay would have a broad utility for monitoring small molecules in food and environment. [GRAPHICS] .